Electricity generating installations, by means of which mechanical energy can be converted to electrical energy for the purpose of providing electricity, are known from the prior art. For the conversion of energy, such installations comprise at least one generator that is driven by one or more rotating machines, for example an internal combustion motor or a gas turbine, for the purpose of generating electricity. The electrical energy provided by the electricity generating installation is fed into an electric consumer grid that is connected to the installation. The feeding-in in this case is effected according to demand, i.e. in normal operation, the electric power provided by the electricity generating installation corresponds to the load demanded by the electric grid. In this case, the rotational machine driving the generator rotates substantially at a constant rotation speed.
If there is a sudden pronounced change in the consumer-side demanded load, it is normally necessary for the operation of the electricity generating installation to be adjusted by appropriate control measures. If, for example, the consumer-side load suddenly collapses, because large consumers or entire parts of the electric grid are switched off, the supplied mechanical energy can no longer be converted to electrical energy to the same extent, and consequently all rotating components of the electricity generating installation begin to accelerate, because of their inherent moments of inertia. Such a sudden collapse of the consumer-side load is also referred to as load shedding.
In order to monitor the operation of the electricity generating installation, one or more operating parameters of the generator and/or of the rotating machine is or are acquired, and checked continuously, or at prescribed intervals, as to whether they lie inside or outside an admissible range. If, for example, the rotational speed of one or more of the rotating components of the installation exceeds an admissible maximum value, counter-measures have to be taken for safety reasons. For example, the supplied energy, in the form of the fuel supply to a gas turbine, may be restricted. In extreme cases, the rotating components have to be switched off completely.
As a counter-measure, a complete switch-off of components of the electricity generating installation, in particular, involves a considerable resource demand. Following a complete switch-off, the electricity generating installation must be restarted, powered-up and synchronized to the frequency of the electric grid to be supplied.
In this case, there is the problem that the counter-measures are in part also initiated in operating situations in which there are only temporary collapses of power, which, over a certain period of time, can be accepted or claimed against, without counter-measures. If such power fluctuations are erroneously identified as load shedding and corresponding counter-measures are initiated, a considerable resource demand is caused needlessly.
In light of this, the efforts in the prior art are toward improving the known methods for monitoring the operation of an electricity generating installation.
DE 103 28 932 A1, discloses a method in which the alternation frequency of the voltage provided by means of the generator of an electricity generating installation is acquired as an operating parameter and compared with an admissible maximum value. The alternation frequency of the voltage is directly proportional to the rotation speed of the generator. In addition to the alternation frequency, a second operating quantity is acquired, which depends on the moment of inertia of the rotational machine. This may be the time change of the alternation frequency. Only if the two operating quantities lie outside a respectively admissible maximum value is it inferred that there is load shedding, and corresponding counter-measures are initiated. The disclosed method accordingly seeks, in the case of a sudden grid load collapse, to take into consideration, besides the rotation speed of the generator, also its acceleration, and to use this as a further indication of the existence of load shedding. Since, if there is actually load shedding, a characteristic acceleration value ensues, this parameter can serve as an additional evaluation criterion.
The known methods have basically proved effective for monitoring the operation of electricity generating installations and identifying load sheddings. However, there is a requirement for further, improved methods that enable differing operating states and malfunctions to be distinguished in a particularly reliable manner.